项目Euler 8 - Haskell

Question

通过Project Euler我将我的解决方案与这里的解决方案进行比较.

对于问题8,我的代码产生正确的答案(通过网站上的校验金确认)23514624000.

module Main where

import Data.List

main = do
    print $ last (sort eulerEight)


eulerEight = doCalc [ x | x <- toDigits 7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450]
    where
        doCalc (_:[]) = []
        doCalc (x:xs) = if 0 `notElem` take 13 (x:xs) && length (x:xs) > 12
                then product (take 13 (x:xs)) : doCalc xs
                else doCalc xs

toDigits n 
 | n < 1 = []
 | otherwise = toDigits (n `div` 10) ++ [n `mod` 10]

我意识到这可能要好得多,所以在这里检查解决方案并且它似乎不正确.

import Data.Char (digitToInt)
import Data.List

problem_8 = do
        str <- readFile "number.txt"
        -- This line just converts our str(ing) to a list of 1000 Ints
        let number = map digitToInt (concat $ lines str)
        print $ maximum $ map (product . take 13) (tails number)

我根据Project Euler网站上的问题更改了take 5的值为13,但是上面的代码产生了错误的答案2091059712.我已经检查了number.txt中的数字是否正确并且它具有两个例子都有1000个数字.任何人都可以阐明产出不同的原因吗？(IM也许想用它做使用的事实tails,而不是tail,但林不知道)

Answer 1

发生的事情是digitToInt返回一个Int,当32增加到13时,它在32位系统上太短而无法容纳测试数字.将其更改为(fromIntegral . digitToInt)并且它正常工作.